PSXII-17 Fiber content in diets for feedlot lambs: carcass characteristics

This is the authors' abstract. We don't add key points for this paper.

The objectives of this trial were to evaluate the effects of levels of fiber in high-grain diets on carcass characteristics of feedlot lambs. Fifty-eight Dorper x Santa Inês ram lambs (initial BW 20.7 ± 1.19 kg and 75 ± 10.83 d old) were assigned to a randomized complete block design. The treatments were defined by the fiber (“Coastcross” hay) content in the diets (CP: 16,12% ± 0.92): 0F: no forage diet (NDF: 10.4%); 5F: 5% of forage (NDF: 12.1%); 10F: 10% of forage (NDF: 15.0%); 15F: 15% of forage (NDF: 15.5%); 20F: 20% of forage (NDF: 20.8%) and 25F: 25% of forage (NDF: 23.5%). The experiment lasted 89 days, at the end of this time, the animals were slaughtered (169 ± 10.83 d old) to evaluate carcass characteristics. There was a quadratic response for slaughter BW (0F: 46.3; 5F: 48.1; 10F: 49.4; 15F: 50.3; 20F: 48.5; 25F: 43.3 kg; P < 0.01), hot carcass weight (0F: 24.8; 5F: 25.6; 10F: 26.0; 15F: 25.7; 20F: 24.3; 25F: 21.8 kg; P = 0.01), cold carcass weight (0F: 24.3; 5F: 25.1; 10F: 25.4; 15F: 25.1; 20F: 23.8; 25F: 21.2 kg; P = 0.01) and longissimus dorsis area (0F: 16.3; 5F: 16.5; 10F: 17.4; 15F: 16.5; 20F: 16.0; 25F: 15.1 cm2; P = 0.04). There was a linear decrease in the hot carcass yield (0F: 53.0; 5F: 53.3; 10F: 52.5; 15F: 50.9; 20F: 50.1; 25F: 50.2%; P < 0.01), cold carcass yield (0F: 52.0; 5F: 52.2; 10F: 51.4; 15F: 49.8; 20F: 49.0; 25F: 48.9%; P < 0.01) and body wall thickness (0F: 16.2; 5F: 17.0; 10F: 16.3; 15F: 16.3; 20F: 15.1; 25F: 13.6 kg; P = 0.01). There was no effect on subcutaneous fat thickness. In conclusion, the diet with up to 5% of forage allowed higher carcass yield; however, the heavier carcasses were produced by the lambs that received 10F diet.